The present invention relates to electric lawn mowers of a type where an electric motor is activated by a battery to rotate a cutter blade within a cutter housing.
Various electric lawn mowers have been known, among which are a battery-powered lawn mower disclosed in Japanese Patent No. 2,837,960 and an electric lawn cutting system disclosed in Japanese Patent No. 2,880,116.
The battery-powered lawn mower disclosed in U.S. Pat. No. 2,837,960 includes an electric motor that is mounted on a vehicle chassis and covered with a shroud and housing having a battery pack accommodated in a container provided on the housing. The electric lawn cutting system disclosed in U.S. Pat. No. 2,880,116 includes an electric motor that is mounted to a lower housing via a metal support plate and covered with a lower portion of an upper housing. In the cutting system, batteries are mounted on the lower portion of the upper housing and covered with an upper portion of the upper housing.
However, in the above-discussed battery-powered lawn mower, a considerable amount of heat of the electric motor tends to be trapped within the shroud and housing, and it is desirable that arrangements be made to allow the heat to effectively escape from within the shroud and housing. Further, in the above-discussed electric lawn cutting system, a considerable amount of heat of the electric motor tends to be trapped in the lower portion of the upper housing, and a considerable amount of heat of the batteries tends to be trapped in the upper housing. Thus, in this case too, it is desirable that arrangements be made to deal with the heat of the batteries and motor in an effective and efficient manner.
In view of the foregoing prior art problems, it is an object of the present invention to provide an improved electric lawn mower which is capable of long-time continuous operation without suffering from the heat of the battery and electric motor.
According to an aspect of the present invention, there is provided an improved electric lawn mower of a type which comprises a machine body section, a rechargeable battery, an electric motor activatable by the battery, and a cutter blade provided within a cutter housing and rotatable via the electric motor to cut the grass. The lawn mower of the invention further comprises a cover member collectively covering the battery and electric motor. The cover member in the invention is shaped to progressively slant upward in a front-to-rear direction of the machine body section, and the cover member has an opening formed in its lower front end portion and an air vent formed in its rear end portion to thereby permit ventilation from the opening to the air vent such that the battery and the electric motor can be cooled by air flows. Such arrangements can effectively prevent the battery unit and motor from overheating, which thereby allows the electric lawn mower to withstand long-time continuous operation or use.
In a specific implementation, the cutter housing defines a communication hole communicating with an interior space defined by the cover member. When the cutter blade is rotating, the communication hole allows an air flow to be produced from the opening and air vent into the cutter housing, while when the cutter blade is not rotating, the communication hole allows a reverse air flow to be produced from within the cutter housing to the air vent due to heat of the battery and/or elecetric motor. This arrangement can promote hear radiation from the battery and motor.